| # DNS |
| |
| This directory contains DNS library which is a modified copy of Chromium's DNS |
| code (net/dns). The current files are taken from milestone M88 of the code |
| with the latest commit hash of `ad67ec1efbf21306b583c4daf34cf2ba4c591237`. |
| |
| DNS library is used by: |
| * Patchpanel's multicast forwarder. |
| * DNS proxy for DNS over HTTPS. |
| |
| It provides DNS functionalities of: |
| * Parsing DNS queries. |
| * Create raw DNS responses from DNS queries' answers. |
| |
| ## Modifications |
| |
| The code here is a modification of Chromium's DNS code. The modification is |
| done to minimize the code imported. Currently, the necessary functions we |
| want are: |
| * `DnsQuery::Parse` (for parsing queries), |
| * `DnsResponse::WriteHeader`, `WriteAnswer`, ... (for writing raw responses). |
| |
| The modification process is done by importing only the necessary functions, |
| followed by importing the minimal amount of code necessary to make the |
| necessary functions work. For example, functionality of writing DNS queries |
| and parsing DNS responses are removed. |
| |
| Below are the changes made: |
| * Namespaces are changed from net to patchpanel. |
| * All the necessary files are flattened into one directory. |
| * Update `NET_EXPORT` with `BRILLO_EXPORT`. |
| * Remove all unneeded functionality. |
| |
| ## Alternatives Considered |
| |
| An alternative is to having a modified copy of the Chromium's DNS code is to |
| port the DNS code to libchrome. Although it avoids having to copy and maintain |
| duplicated code, it has the downsides of needing to continuously update the code |
| alongside *libchrome* uprevs and having to include the whole DNS code. |
| |
| Another option would be to use a low level library like *libbind9*. One |
| disadvantage of going with this approach is introducing additional payload |
| by adding the development package. The API of the library is also fairly |
| complicated and prone to introducing semantic bugs. |
